The present invention relates generally to cleaning devices and more particularly to apparatus for removing deposits from the interior walls of process vessels such as, for example, digester vessels used in aluminum production.
Typically, such digesters are large, cylindrical vessels having a diameter of about thirteen feet and a height of about fifty-five to seventy feet, or more. A hard, glass-like scale builds up gradually over time on the interior walls of the digester vessel and can reach thicknesses on the order of six inches. Heretofore, the removal of such hard deposits has been extremely labor intensive, dangerous and time consuming due to the physical configuration of the digester vessel and the limitations imposed by manually operated tools and by known scaffolding or like rigging. Limited access to the interior of a typical aluminum process digester vessel also presents problems. Due to the restricted opening afforded by the access manhole formed in the top wall of the vessel, usually about twenty-one inches in diameter, only relatively small, light-duty tools and related rigging of limited physical dimensions and weight can be introduced into the interior of the vessel. Additional limitations on clear or open work space within the vessel interior are also caused by a central shaft and radial paddles which extend vertically along the central axis of the vessel.
The present invention solves many of the problems heretofore encountered in cleaning cylindrical digester or other process vessels of the type discussed above. The present invention provides a cleaning apparatus which greatly reduces the time and expense of cleaning the interior walls of such vessels while concurrently producing a cleaner wall and creating a safer work environment for the laborer than heretofore possible.
The present cleaning apparatus includes a stable, vertically moveable work platform carrying a pivotal and extensible impact tool for accessing essentially all of the interior surface of the vessel. The apparatus of the invention also provides a heavy-duty impact tool which has high power capabilities for removal of very thick and hard deposits which was not possible with prior hand-held tools.
Still further, the cleaning apparatus of the present invention provides a stable construction comprising a plurality of prefabricated structural sections which, in a disassembled state, are of a size to conveniently pass through the restricted access manhole of the vessel for relatively fast and easy assembly once inside the vessel. Once assembled and mounted inside the vessel, the invention provides a moveable work platform for carrying the heavy-duty, powered impact tool with a novel clamping arrangement to provide firm support for the tool and a quick release feature to permit passage around the paddles.